Continuous subcutaneous delivery of medication or monitoring of a body analyte is often accomplished using a cannula, which remains in the body of a patient for several days. Diabetes patients may use such cannula positioned in a subcutaneous compartment for continuous delivery of insulin effectuated by pumps and/or for monitoring interstitial glucose levels by means of sensors. A combination of a tube, connecting an insulin pump to the cannula and a detachable connector is often referred to as an infusion set. Such infusion sets and modes of their insertion are discussed in, for example, U.S. Pat. Nos. 4,755,173, 5,176,662 and 5,257,980. Subcutaneous cannula insertion modes for continuous glucose monitoring are discussed in, for example, U.S. Pat. Nos. 5,390,671, 5,568,806 and 5,586,553. Usually trans-cutaneous (“hypodermic”) cannula insertion can be carried out with the aid of a sharp metallic “penetrating member” to be withdrawn after piercing the skin. This procedure can be carried out manually by the patient. The insertion is usually painful and may require considerable skill. Some patients are reluctant or hesitant to pierce their own skin, and therefore achieving proper insertion of the cannula may be difficult. Another hurdle of currently existing methods of manual or automatic cannula insertion is a possibility for unintentional self piercing. Conventional systems have a further problem associated with a need for a proper bio-hazard disposal of the cannula. Such difficulties can be attributable to insufficient patient's manual dexterity or alternatively to his or her anxiety associated with anticipated discomfort as the needle pierces the skin. This problem can be especially significant when an insulin pump is used since misplacement of the cannula can cause kinking along the cannula, incorrect cannula insertion angle or incorrect cannula insertion depth leading eventually to cannula obstruction. As a result of this, delivery of insulin could be hampered causing a life threatening situation.
In an attempt to cope with this problem, automatic infusion set insertion devices (“inserters”) were developed to assure correct placement of a cannula in the body of the patient (i.e., subcutaneous layer), at a correct angle, while minimizing pain and hazardous obstructions associated with cannula insertion. U.S. Pat. Nos. 6,093,172 and 6,830,562 disclose inserters having a spring-loaded plunger for an automatic subcutaneous placement of infusion sets. These automatic inserters can be used with “pager like” insulin infusion pumps having long tubing and a cannula. However, these devices cannot be used for insertion of a cannula that is employed in skin adherable insulin pumps, which do not employ long external tubing. An example of such device is disclosed in U.S. Pat. No. 6,699,218 to Flaherty et al. In this skin adherable insulin delivery device, the cannula is rigidly connected to the pump's housing. After adhesion of the device to user's skin, the cannula is fired, i.e., it emerges from the device's housing and pierces the skin. Consecutively, the penetrating member is retracted back into the pump's housing.
One of the disadvantages of this device is that it is relatively bulky, heavy and indiscreet because the spring loaded mechanism is enclosed within the device's housing during the entire period of usage. In addition, the cannula has only one length, and it can penetrate the skin at only a certain angle. Further, the patient cannot adjust these parameters according to various insertion sites and other clinical requirements.
Continuous glucose monitors are disclosed in U.S. Pat. Nos. 5,390,671 and 6,143,164, assigned to MiniMed and E. Heller & Company, respectively. These devices monitor glucose levels within the subcutaneous compartment by a sensor that is insertable manually or automatically, as discussed in U.S. Pat. No. 7,110,803, assigned to DexCom, in a similar manner as is inserted a cannula for drug delivery.
In view of the foregoing, it would be desirable to provide improved systems and methods for protecting and concealing needles for use in inserting cannulae and/or sensors into the body of a patient.